1. Field of the Invention
The present invention relates generally to systems and methods for collecting and distributing traffic information, and more particularly to a traffic information collection and distribution method, a traffic information collection and distribution system, a center apparatus, and a vehicle-installed terminal apparatus, for collecting and distributing traffic information based on probe data acquired by a sensor installed in a vehicle.
2. Description of the Related Art
Conventionally, probe cars are often used to acquire road traffic information. A probe car is a vehicle having various sensors and a vehicle-installed apparatus. The vehicle-installed apparatus includes a communication apparatus, etc. The probe car collects data, such as vehicle position, travel speed, travel distance, etc. (such data will hereinafter be referred to as “probe data”) by means of the sensors, and transmits the collected probe data to a predetermined traffic information center by means of the communication apparatus. Any cars may be configured to serve as probe cars; to give a common example, taxis may be utilized as probe cars, with the cooperation of a taxi company.
Meanwhile, the traffic information center processes the probe data transmitted from the probe cars and collects traffic information, such as travel time between intersections, traffic congestion locations, traffic congestion lengths, etc. However, in actuality, because the number of probe cars is insufficient, there is a problem of accuracy of the collected traffic information. Thus, for example, there is an idea of making vehicles that have a navigation apparatus with a communication function serve the role of probe cars to increase the number of probe cars. Many present vehicles already have the sensors necessary for collecting traffic information, and it is predicted that navigation apparatuses with a communication function will increase further in the future.
When a large number of vehicles thus become probe cars and probe data are transmitted to the traffic information center from such a large number of probe cars, problems that differ from the conventional case occur. A first problem is that because probe data are transmitted from a large number of probe cars, the communication load on the communication line and the processing load on a computer of the traffic information center become enormous. A second problem is how different data on the same event on a road (for example, a traffic congestion at a certain location) that are transmitted from a plurality of probe cars should be classified or identified as being equivalent.
JP 2003-296891 A (Patent Document 1) discloses an example of a probe car, a vehicle-installed apparatus of which performs event detection, called “SS/ST,” to reduce the data transmitted to a traffic information center. “SS (short stop)” refers to a stop state in which the speed of the vehicle is less than a predetermined speed, “ST (short trip)” refers to a travel state in which the speed of the vehicle is no less than the predetermined speed. Each time when an SS or ST event ends, the vehicle-installed apparatus uplinks the event status and probe data, such as the vehicle position, vehicle speed, etc. Hereupon, ‘uplink’ refers to data transmission from the vehicle-installed apparatus to the traffic information center. The “SS/ST” is an event-driven uplink method, and it has been shown that this method advantageously produces the effect of compression of the uplinked data.
In regard to the second problem mentioned above, a general method for resolving similar problems, e.g., adaptive resonance theory (ART), can be applied. That is, a computer configured to process probe data learns using training data that have been set in advance and forms clusters of data similar to the training data. Probe data that are input in real time are then matched with the clusters to detect and classify events.
However, with the event detection by SS/ST according to Patent Document 1, when there are differences in event detection conditions (such as travel circumstances and circumstances of the surroundings of vehicles), differences in vehicle type, differences among individual vehicles, differences in sensor type, differences among individual sensors, etc., large differences may arise in the probe data, which may thus make it difficult to merge (unify) events in the traffic information center. Also, even when information is compressed by SS/ST, we cannot expect the amount of uplinked information to be reduced because probe data are uplinked on all event occurrences under circumstances where the increase in the number of the probe cars and in the types and time resolution of sensors progresses.
If the adaptive resonance theory could be applied to probe data obtained by vehicles, the characteristics and order of the data subject to analysis would vary diversely within short time periods according to the number of vehicles, differences among individual vehicles, road travel characteristics, etc. Thus, unlike an application where the sensors for use in judgment are specified in advance, the setting of training data and the forming of clusters of data cannot be performed easily. In the least, it is difficult to perform real-time detection and classification of events from probe data that are input in real time.
It would thus be deemed desirable to provide a traffic information collection and distribution method, a traffic information collection and distribution system, a center apparatus, and a vehicle-installed terminal apparatus that can reduce the amounts of probe data uplinked from probe cars, and that can perform the process, in real time, of extracting similar feature data from a large number of probe data for a specific road section, associating event information concerning a traffic condition with the road section corresponding to the extracted feature data, and distributing the event information for the specific road section.
Illustrative, non-limiting embodiments of the present invention overcome the above disadvantages and other disadvantages not described above. Also, the present invention is not required to overcome the disadvantages described above, and an illustrative, non-limiting embodiment of the present invention may not overcome any of the problems described above.